A number of techniques are known for use in alternative power sources based on solar energy. For example, solar cells are often used to convert solar energy into electricity. Examples of these devices are found in remote locations to power pumps, lights, telecommunication devices and the like. There are also devices that utilize solar energy, such as water heating devices. Solar collector systems employ large reflectors, or arrays of smaller reflectors supported by means of a suitable framework. The reflectors of such systems employ photovoltaic solar panels and more recently parabolic solar troughs. The troughs retain a plurality of curved mirrors in order to concentrate sunlight on glass and steel receiver tubes. Fluid circulating through the tubes can reach temperatures as high as 750 degrees Fahrenheit and can be used in order to generate steam, which drives a turbine and generator to produce electricity.
The effectiveness of these devices is generally improved if the device can track the position of the sun in order for the device to absorb as much energy as possible. Therefore, such devices also generally include some form of solar tracking apparatus in order to track the relative position of the sun wherein the collector is incrementally moved in concert with the sun in order to maintain alignment.
To effectively concentrate solar energy in the operation of any of such systems, the solar concentrator or parabolic trough must rotate azimuthally each day from a generally east-facing direction at sunrise to a generally west-facing direction at sunset. It is also advantageous to place the solar concentrator or trough in a downward facing direction when stowing the solar collection system when the system is not operating (i.e., at night) and/or in a repair or service position.
The installed cost of the actuation/drive system used in connection with solar collection systems is a major driver in terms of their requirements. A key to the success of solar power systems is reducing the capital expenditure for the power plant owners while maintaining efficient and repeatable operation. As noted, requirements for solar collectors include an angular range of motion of 180 degrees for sun tracking and 240 degrees total for enabling storage and maintenance of the collector trough, in the case of a parabolic trough. Moreover, the actuator system must be configured to tolerate high torque capacities based on normal operation including normal wind and environmental loads, as well as loads created during the intended operational life of the system, while also guaranteeing positional accuracy (e.g., 0.1 degrees).
Electromechanical drive systems have been considered for use in solar collector systems in which a motor enables rotary motion through a geared transmission, this motion being imparted to the trough or concentrator portion of the collector. A functional benefit is that such systems permit continuous motion, but the costs for gear-driven assemblies, whether these assemblies are purchased as standard products or are specifically designed for implementation, have been determined to be prohibitive and therefore a major impediment to successful implementation of such drive systems.
There is required a drive system for a solar collector that enables a collector(s) to be effectively, accurately and repeatably driven while being effective in terms of its manufacturability and overall cost.